The traditional manner of communication switching is circuit switching. It involves the allocation of some amount of bandwidth (the "circuit") to a communication during formation of a connection for the communication through the switch, and keeping that bandwidth allocated to that communication (i.e., keeping the connection "up") constantly for the duration of the communication. Conventional circuit-switching is not suited for handling of communications that require a bandwidth other than a fixed predefined bandwidth which the switching system has been designed to allocate to every communication. Hence, it is not suited for handling communications that occur at a variety of transmission rates, and particularly not those that occur at a rate higher than the predetermined fixed rate.
To avoid this problem, packet switching has been introduced. Unlike circuit switching, packet switching allocates bandwidth to a communication dynamically and only when the bandwidth is needed. Therefore, it is able to handle communications that occur at a variety of rates. However, packet switching is not without problems of its own. For example, it is not suited for providing services that require continuous and ordered signal transmission and delivery, such as voice and video communications.
A further difficulty with the two abovementioned approaches to switching is their unsuitability for providing broadcast services. On the one hand, braodcasting often causes blocking in conventional circuit switches. On the other hand, broadcasting often causes intolerable or at least undesirable delays of other communications in packet switches.
With the advent of integrated services digital networks (ISDNs), it has become possible to provide a variety of communication services in a single communication network. However, ISDNs presently operate at low transmission rates--typically 64 Kbps per communication--and typically make use of conventional packet and/or circuit switches. Consequently, they are subject to the constraints of those switches enumerated above.
In order to expand the range of services that can be provided by ISDNs, numerous efforts are under way to expand the transmission rates at which they operate into the Mbps range i.e., to develop broadband ISDNs (BISDNs). Unfortunately, the abovementioned problems of conventional circuit-and-packet-switching systems become even more acute at these rates. Consequently, what the art requires is a switching suitable for use in BISDNs that overcomes the problems of the conventional circuit-and-packet-switching systems.